The Monday night fire at the Fitz Apartments, 1747 Peoria St., killed a married couple and injured 25 others.

Witnesses told 7NEWS they saw a man with a gas can in the area of the apartment at the time the fire started.

Sources familiar with the investigation told Hernandez the person of interest is a tenant in the apartment building next to the four-story building that burned.

"Detectives have interviewed this person however not enough probable cause exists to make an arrest. As a result of this interview his mental health was a concern and he was referred to professionals for further evaluation," said Sgt. Cassidee Carlson, Aurora police public information officer. "We have no reason to believe that the public is at risk. Due to privacy concerns and the on-going investigation, I cannot elaborate to further detail."

A tenant told Hernandez that investigators have placed a red evidence seal on the door of an apartment unit where the person of interest lives.

The Aurora police Major Crimes Unit is working closely with arson investigators on the case.

Earlier this week, the owner of the apartment complex said he suspected the fire was not an accident.

"We have our suspicions as to who may have caused this," the owner, who didn't want his name used, told 7NEWS. "There's too many factors about it... It wasn't coincidental."

Detectives are interested in any information that the public may have involving the fire. If you have any information you are asked to call the tip line at 303-739-6118. If you would like to remain anonymous you may call Crime Stoppers at 720-913-7867.